Probiotics in the treatment of Japanese cedar pollinosis: a double-blind placebo-controlled trial

Summary Background Probiotic bacteria may be effective in the treatment of allergic inflammation and food allergy, but efficacy and underlying mechanisms remain unclear. Objective The present study investigated the effects of probiotic strain Bifidobacterium longum BB536 in the treatment of Japanese cedar pollinosis (JCPsis). Methods In a randomized, double‐blind, placebo‐controlled trial, 44 JCPsis subjects received BB536 or placebo for 13 weeks during the pollen season. Subjective symptoms and self‐care measures were recorded daily and blood samples were taken before and during intervention to measure blood levels of parameters related to JCPsis. Results BB536 intake was associated with a significant reduction in number of subjects prematurely terminated due to severe symptoms and pollinosis medication (P=0.0057 vs. placebo group). Comparison of subjective symptom scores indicated significant decreases in rhinorrhea, nasal blockage and composite scores in the BB536 group compared with the placebo group. Comparison of medical scores showed marked improvements in all symptoms on BB536 intake. A T‐helper type 2 (Th2)‐skewed immune response occurring along with pollen dispersion was observed. BB536 significantly suppressed increases in plasma thymus‐ and activation‐regulated chemokine and tended to suppress elevations of Japanese cedar pollen (JCP)‐specific IgE. Conclusion These results suggest the efficacy of BB536 in relieving JCPsis symptoms, probably through the modulation of Th2‐skewed immune response.